The objectives of this project are to survey the range of mycoplasma viruses, to characterize the biology of these viruses, and to examine the possible role of these viruses in human disease. The structure and growth of the three mycoplasma virus groups will be studied. The structural studies will concern the viral DNA and protein compositions and electron microscopy of the particles. The growth studies will concentrate on the assembly and extrusion of Group L1 and L2 viruses and the nature of cell lysis caused by Group L3 virus. The role of the cell membrane in virus release will be examined by freeze- etching. The medical aspects of mycoplasma viruses to be examined will be the nature of the carrier state, the viral flora of M. pneumoniae, virus neutralization, and the affect of these viruses on tissue culture cells.